PROJECT SUMMARY More than 5 million Americans live with heart failure (HF), a serious condition with 5-year mortality rates of 50% and medical care costs reaching almost $40 billions nationally. Although pharmacological treatment reduces mortality and costs, over half of HF patients do not take their medications regularly. Poor medication adherence results in worse clinical outcomes and additional costs. Studies designed to improve adherence have had mixed results and have often employed complex interventions with low scalability and sustainability in clinical settings. The American Heart Association and the American College of Cardiology have recently highlighted the need to develop novel, highly scalable interventions to improve medication adherence and clinical outcomes in this high-risk population. This application, designed in response to PA-14-335 ?Advancing Interventions to Improve Medication adherence?, seeks to study the possible role of mindfulness training, (MT), a behavioral intervention aimed at developing increased attention and awareness of moment-to-moment experiences, in the promotion of medication adherence among patients with HF. There is evidence supporting the efficacy of MT in improving patient-level factors that are associated with poor medication adherence in this population (i.e., memory and attention deficits; depression). Preliminary, observational findings generated by our group and others show that higher mindfulness skills are associated with better medication adherence and that self-reported medication adherence improved after class-based MT in a small group of patients (n=8) with stable cardiovascular disease. Our preliminary work has also shown that MT (usually delivered in a class- based format) can be successfully phone-delivered by trained instructors with great potential for scalability. No study, however, has yet formally explored the role of MT in improving medication adherence. We propose to use this exploratory funding mechanism to conduct a prospective, pre/post design study among 50 stable outpatients with class I-III HF and suboptimal medication adherence (Morisky scores <6). MT sessions (one individual 30-min session/week for 8 weeks) will be phone-delivered by qualified mindfulness instructors. Data will be collected at baseline, 2- (intervention completion), and 6 months since baseline. The primary outcomes will be feasibility and acceptability. Secondary outcomes will be changes in medication adherence (multi-modal assessments including objective and self-reported measures of adherence and functional status, a clinical marker of medication adherence). Exploratory outcomes will be changes in cognitive function, depressive symptoms, and mindfulness skills. We hypothesize that phone-delivered MT will be feasible and acceptable to patients with HF and will improve adherence to medications. In addition, we expect to observe improvements in cognitive function (and, possibly, mindfulness and depressive symptoms), and that such changes will be associated with improvements in medication adherence. If the efficacy of phone-delivered MT in improving medication adherence is proven in a future large RCT, it will be easily disseminable to primary care settings.